1. Field of the Invention
This invention relates to an improved electric fence wire construction for use by cattlemen, farmers, and others. Electric fence wire constructions carry an electric charge which shocks animals upon contact with the outer surface of the construction and tends to prevent their crossing the fence. These constructions are strung from fence posts or other convenient attachment points. They may be used as perimeter fencing to enclose animals or to keep out predators. They may also be used to subdivide pastures temporarily to insure that they are grazed uniformly, in which case the electric fence wire construction may be taken down and restrung every few days forcing animals to graze different strips of land in regular rotation.
The electric fence wire construction of this invention comprises both support members and conductive members which should have several inter-related, special characteristics to perform well. The wire construction should be abrasion resistant, sufficiently light in weight to be portable, and flame resistant (that is to say, self-extinguishing or unable to support combustion). It should be reasonably flexible, yet strong, should knot without breaking, and should hold a knot without slipping. Because these wire constructions may be relocated several times, they should resist wear not only while in use, but also during handling when they are taken down and put up for relocation to another site. The conductive members should have a high degree of conductivity and be sufficiently malleable to perform satisfactorily in splicing. Furthermore, electric fence wire constructions should retain these properties when subjected to extremes of weather and temperature over long periods. For example, the wire construction should resist fading, corrosion, and loss of strength in blizzards at less than -50.degree. F. (-46.degree. C.) and direct sunlight at above 100.degree. F. (38.degree. C.), and have a low coefficient of linear expansion to resist contraction when cold and sagging when warm.
2. Description of the Prior Art
For several years the prior art has been typified by single component constructions of galvanized steel wire, which are sufficiently thick to serve both conducting and supporting functions simultaneously, and by a plied, rope-like combination electric fence wire construction in which an olefin fiber such as polyethylene or polypropylene fiber serves as the supporting member and stainless steel wire serves as the conducting member. U.S. Pat. No. 3,291,897 (Bramley) shows an example of this latter construction.
These prior art electric fence wire constructions suffer several drawbacks, which as far as we know the art has not solved in the seventeen years since the Bramley Patent issued. The single component steel wire constructions, while strong, are too heavy for easy portability and installation and hence are impractical in many situations. In the combinations of olefin supporting members with stainless steel, the stainless steel wire construction when spliced or knotted has heated sufficiently to cause fires. To compound this problem, flames have been carried along the length of the wire construction by prior art supporting members, spreading the fire to adjacent fields or buildings. These prior art supporting members have also been subject to loss of strength upon exposure to weather, particularly to the ultraviolet rays in sunlight. Furthermore, olefin fibers do not hold a knot well; the ability to hold a knot is important, for example, when splicing the beginning of one package of electric fence wire to the end of another or when repairing a break.
Composite electric fence wire constructions of the prior art have occasionally been made with tinned copper as the conductor, which eliminated problems of low conductivity but was too weak to withstand breakage during use, and particularly during winding and unwinding the wire construction during temporary installation. Hence, as far as we know tinned copper is used little if at all.
We have noticed an additional problem in prior art combination electric fence wire construction when made for example from stainless steel supported by a conventional olefin. When stretched during installation or use, the conducting member may break while the supporting member remains intact. It is then difficult to locate the particular section of the electric fence wire construction which needs replacing.